1. Field of the Invention
The present invention relates to an exposure method and apparatus which exposes a photosensitive substrate with a pattern image of a mask used in a photolithographic process for manufacturing micro devices such as a semiconductor device, liquid crystal display device, image pick-up device (CCD), thin-film magnetic head, opto-magnetic disc, etc.
2. Related Background Art
Conventionally, a projection exposure apparatus of a step-and-repeat type (stepper, or the like) which positions shot areas in an exposure field of a projection optical system successively by stepping of a wafer and collectively exposes the shot areas with a pattern image of a reticle is used as an exposure apparatus for transferring a reticle pattern serving as a mask onto a wafer (or a glass plate) on which a photosensitive material (photo-resist) is coated. In a projection exposure apparatus of this type, a driving device of a feed screw system was chiefly used as a driving device for driving a wafer stage or a reticle stage, conventionally. Recently, however, in order to improve the throughput (productivity) by reducing a positioning time and to lower an oscillation by a non-contact drive, a linear motor become to be used as a driving device therefor.
As an exposure apparatus for transferring a pattern image having a larger space onto a wafer without expanding the exposure field of a projection optical system, a projection exposure apparatus of a step-and-scan type which performs exposure by synchronously scanning a reticle and a wafer with respect to a projection optical system after stepping each shot area on the wafer to a scan start position is employed. The exposure apparatus of the scanning exposure type is disclosed, for example, in U.S. patent application Ser. Nos. 139,803 (Oct. 22, 1993) and 274,037 (Jul. 12, 1994). When the scanning exposure apparatus is of a reduction projection type, since it is required to scan (especially a reticle) with high speed, it is preferably to use a linear motor at least as a driving device for a reticle stage. It is also preferable to also drive a wafer stage by the linear motor in order to perform more stable scanning.
Conventionally, a linear synchronous motor of a permanent magnet type, electromagnet type, or the like, is used as a linear motor for driving a reticle stage or a wafer stage of an exposure apparatus. This linear synchronous motor basically consists of an armature coil on the primary side and a field magnet on the secondary side, and is arranged such that a mover side is moved by a moving magnetic field which is generated in said armature coil. In this case, it is required to detect the position of the field magnet on the secondary side in order to correctly determine the phase of the moving magnetic field generated in said armature coil (in order to conduct phase switch correctly). Then, in the conventional exposure apparatus, the linear synchronous motor is provided with a phase switching sensor (consisting of a magnetic sensor of a Hall element type) for detecting a positional relation of the polarity of the field magnet with respect to the standing armature coil. In the exposure apparatus, there is also provided a coordinate measuring device (laser interferometer, or the like) for detecting the position of a stage. However, the coordinate measuring device is provided in parallel to the phase switching sensor in the conventional exposure apparatus.
As described above, when the linear motor is used as the driving device for driving the stage in the conventional exposure apparatus, the phase switching sensor is provided separately from the coordinate measuring device for the stage. This phase switching sensor is required to be disposed, for example, periodically, on the entire range in which the field magnet moves, which results in an inconveniently complicated mechanism and wiring of the stage.
Since, generally, various mechanisms such as an alignment sensor, a focal position detecting system for autofocusing, and a loader system, for a reticle or a wafer, are incorporated in an exposure apparatus, it is desired to constitute a driving mechanism for the stage as simple as possible and to secure a space around the stage as wide as possible.
An object of the present invention is, in an exposure apparatus using a linear motor as a driving device for driving a stage, to drive said linear motor without using a special phase switching sensor.
A first exposure apparatus according to the present invention comprises a mask stage for positioning a mask, a linear motor for driving said mask stage, and a position detection system for detecting the position of said mask stage, and uses an output signal from the position detection system as phase control information for said linear motor.
A second exposure apparatus according to the present invention comprises a substrate stage for positioning a photosensitive substrate, a linear motor for driving said substrate stage, and a position detection system for detecting the position of said substrate stage, and uses an output signal from the position detection system as phase control information for said linear motor.
In the first and second exposure apparatuses, said position detection system is, for example, a laser interferometer.
According to the first and second exposure apparatuses of the present invention, the linear motor, such as a linear synchronous motor, is used as a driving device for driving the mask or the photosensitive substrate, and the position detecting system of the stage is used as the phase switching sensor for detecting the position of the field magnet of the linear synchronous motor. Specifically, a positional relation between the armature coil and the field magnet of the linear motor for driving said stage is detected on the basis of an output (a result of measurement) of the position detection system of the stage. For example, when the field magnet and the armature coil of said linear synchronous motor are in a predetermined positional relation, a measured value by said position detection system is reset (or preset), and thereafter the measured value by said position detection system is divided by an alignment pitch of the field magnet to obtain a remainder, whereby the positional relation (phase) between said field magnet and said armature coil can be obtained. Accordingly, said linear motor can be driven without provision of another switching sensor. As a result, the manufacturing cost can be reduced, the stage mechanism can be simplified, and other mechanisms can be loaded easily.
In addition, when the laser interferometer is used as the position detection system, the position of the stage can be detected without contact at a high precision, and the phase control between the armature coil and the field magnet of the linear motor can be performed with very high resolving power and a high precision.